1. Mutations

2. Mutations Defined: a change in an organism’s DNA
Where: DNA or Chromosomes
When: During replication, Synapses, or Crossing-Over
Mutations can affect a single gene or an entire chromosome:
Some gene mutations change phenotype (physical characteristics)
Example: Can cause a premature stop codon
Some gene mutations don’t change phenotype.
Example: Could be silent or occur in a non-coding region

3. Gene: Point Mutations A C A G T G T G T C A A A U G U C A A C C A G U
DNA U G U C A A C C A G U U U
mRNA
Amino acids
cysteine
histidine
glutamine
glutamine
phenylalanine
Defined: one nucleotide is substituted for another
Often repaired by DNA Polymerase (spellchecker) enzyme
May lead to amino acid change (see animation)
May not lead to any change (Silent Mutation)
Ex: DNA “CCC” is mutated into “CCG”
Same amino acid is created (glycine)

4. Gene: Frame Shift Mutation (deletion)C A G T G G T C A A A C
DNA U G U C A C C A G U U U G
mRNA
Amino acids
cysteine
histidine
histidine
glutamine
serine
phenylalanine
leucine
Defined: Insertion/deletion of a nucleotide
Entire sequence of DNA/RNA after the mutation is shifted (see animation)
Much more serious to the structure/function of the final protein
mRNA sequence may have early or late “stop codons”

5. Gene: Frame Shift Mutation (insertion)C A G T C G G T C A A A
DNA U G U C A G C C A G U U U
mRNA
cysteine
histidine
glutamine
phenylalanine
Amino acids
glutamine
proline
valine
Defined: Insertion/deletion of a nucleotide
Entire sequence of DNA/RNA after the mutation is shifted (see animation)
Much more serious to the structure/function of the final protein
mRNA sequence may have early or late “stop codons”

6. Impact on Offspring Somatic cell mutations Germ cell mutations
Affect only the individual
May be passed to future generations (either harmful or beneficial)
Not passed on to future generations
Ex: Sperm cell mutation
Ex: Muscle cell mutation
Natural selection often removes mutant alleles from a population when they are less adaptive.

7. Mutation Causes Mutagen: agents in the environment that can change DNA
Speed up replication process
Break apart nucleotides
Ex: UV sunlight breaks hydrogen bond between thymine (T) and adenine (A)

8. REview What is a mutagen and how do they cause problems?
How are proteins affected if the DNA code is mutated?
Example: ATTCGAGG is mutated to ATTCGTGG
What is the difference between a point mutation and frame shift mutations?
When are mutations passed on to future generations?
Are all mutations considered bad/dangerous? Explain.